I think part of this is bad translation, at least that's the case with Polish-English translation. Word "friend" is usually translated as "przyjaciel", but it really should be translated as "znajomy" or at most "kumpel", and "przyjaciel" should be translation of "best f*ing friend".

You couldn't possible have 20 "przyjaciel"s and spend enough time with them to keep the relationship alive. Same with BFFs. You can easily have 50 "kumpel"s and same with friends.

Keeping this mistranslation in mind I think European (or at least Polish) culture isn't much different from American regarding friendship.